Capos are used to engage the strings of a stringed instrument at a given neck position prior to performance, thus allowing a musician to raise the default pitch of a given set of strings without having to dedicate a finger to depressing the given set of strings. (In this application, to “engage” a string is to press the string downward against a fret or a fingerboard so that its pitch is changed.) For example, a musician may use a capo to depress all of the strings of a guitar at the first fret. A musician may also use a capo to selectively engage certain strings, while leaving other strings disengaged. For example, it is frequently advantageous for the low E string to be left disengaged while the other strings are engaged by a capo, commonly called “dropped-D tuning.”
Conventional capos allow certain strings to be engaged when the capo is fitted to the neck of the instrument. However, it would be difficult or impossible for a musician to use a conventional capo to set a first set of strings as engaged by default and a second set of strings as disengaged by default, and then to selectively engage and disengage during a performance a subset of the second set of strings at the neck position occupied by the capo. The subject matter claimed here solves this problem.